It is known in the art to provide tamper proof closures for containers which provide a visual indication of tampering. For example, there is provided, a closure with an interconnected annular band which is detachable from the closure upon first removal of the closure from a container. Such bands normally include a means which engages with a portion of the neck of the container, thus restricting axial movement of the band from the neck of the container once placed in position. Difficulties have been encountered with the use of such tamper evident closures when used on containers manufactured within the limits of normal dimensional tolerances. It has been found that with manufacturing variation of the container neck, within allotted tolerances, difficulties are encountered for larger and smaller toleranced container necks. Thus, if the diameter of the container neck is too large, there are difficulties in placing the tamper proof closure onto the container. Alternatively, if loosely fitted, the closure can be removed from the container without severing the band portion. In the past this difficulty due to variation within normal tolerances has necessitated the utilization of expensive manufacturing methods for containers to be used with such closure members.
Patents in the prior an have attempted to address this problem. For example, U.S. Pat. No. 4,732,289 to Granat et al. entitled TAMPER INDICATING CLOSURE MEMBER FOR CONTAINER issued Mar. 22, 1988 describes a tamper indicating closure having a tamper band with an annular flap which folds up along an inner surface of the tamper band when the closure is applied to a container. When an attempt is made to unscrew the closure, the tamper band is resisted by the annular flaps which abut under a portion of an annular bend on the neck of the container. The resistance from the bend provided on the flaps is intended to separate the tamper band from the closure. Because of the varying tolerances of the containers, however, it is possible to manipulate the flaps of the tamper band in order to remove the closure without activating the tamper mechanism.
U.S. Pat. No. 5,310,069 to Ingram et al. entitled TAMPER INDICATING PACKAGE and issued on May 10, 1994 discloses a tamper indicating package comprising a container having a neck with a threaded finish, an annular bead on the neck, a plastic closure which includes a base wall and a depending peripheral skin having threads interengaging the threads of the container, and a tamper indicating band attached to the skirt by a plurality of weakened portions defining a line of severing. An annular flange extends axially upwardly and inwardly from the tamper indicating band toward the base wall of the closure and comprises a first continuous annular flange portion connected to the band by a hinge portion and a second portion which has free ends of the segment portions engaging beneath the bead on the container when the closure is threaded onto the container. In one form, the second portion comprises plurality of segment portions extending upwardly and inwardly from the first continuous portion. In another form, the second portion comprises a second continuous flange portion. The flange is bent intermediate its ends so that the second portion extends inwardly at a greater angle than the first continuous flange portion.
U.S. Pat. No. 4,801,030 to Barriac, entitled TAMPER INDICATING CLOSURE AND PACKAGE discloses a device comprising a one-piece molded closure of plastic which threads onto a container such that when the closure is unthreaded, a tamper-indicating band becomes separated from the lower end of the closure skin. The tamper-indicating band is joined to the closure along a weakened frangible line. A flexible annular wall is formed within the band and extends inwardly and upwardly when the closure is applied to container finish. The band further includes a plurality of circumferentially spaced flexible walls extending circumferentially and fastened at their circumferentially ends to the inner surface of the annular wall and having portions intermediate their ends which extend radially inwardly. When the closure is applied to the container, the intermediate portions of the circumferentially extending walls are flexed radially outwardly intermediate their ends over the annular bead on the container and then flex radially inwardly beneath the annular bead while the annular wall is interposed between the skirt of the closure and the annular bead on the container. When the closure is unthreaded, the upper edges of the circumferentially spaced circumferential walls engage the underside of the bead and cause the band to sever along the weakened line.
The real world problems encountered when dealing with containers having finish areas of varying dimensional tolerances, however, are not adequately addressed. In practical situations the tamper bands of the prior an can be manipulated outward with a small diameter probe or other like object and then over the resisting annular bead of the container in order to defeat the tamper-resistant mechanism.
It is therefore an object of the present invention to provide an improved tamper evident closure member for use with screw-top containers which is adapted for tamper evident operation despite severe dimensional tolerances in the neck of the container.
It is further an object of the invention to provide a completely reliable tamper proof closure which eliminates the possibility of pryable removal over an annular bead on the container without detection.